1. Field of the Invention
The present invention relates to a catalyst employed for producing carbon from mixed gas containing a carbon source.
2. Description of the Prior Art
In general, a carbon material such as graphite has been produced by heating an organic compound under ordinary pressure in an inert atmosphere for carbonizing the same or through incomplete combustion of hydrocarbon gas. However, production of carbon through combustion of hydrocarbon gas is problematic in consideration of shortage of the raw material, i.e., hydrocarbon gas, resulting from exhaustion of global resources, or global warming caused by carbon dioxide gas generated in combustion of hydrocarbon gas. Reduction of carbon dioxide release causing global warming is demanded on a world-wide scale.
In order to effectively utilize carbon dioxide, there is a method of producing carbon from carbon dioxide gas with a metallic catalyst. For example, Japanese Patent Laying-Open Gazette No. 63-104652 (1988) discloses a method of producing carbon from carbon dioxide gas and hydrogen gas with a catalyst of a transition metal such as Fe, Ni or Co.
However, such a transition metal catalyst is inferior in carbon producibility. While the method described in the Japanese Patent Laying-Open Gazette No. 63-104652 increases the surface area of the transition metal catalyst by oxidizing thereby improving carbon producibility in order to solve this problem, the ability of the catalyst is not yet remarkably improved. Furthermore, this method requiring a high reaction temperature of 900 to 1000xc2x0 C. is still insufficient in consideration of effective utilization of energy.
Accordingly, an object of the present invention is to improve carbon producibility of a catalyst for producing carbon mainly composed of a transition metal.
The present invention provides a catalyst for producing carbon, which is employed for producing carbon by coming into contact with mixed gas containing a carbon source. The catalyst is mainly composed of at least either nickel or cobalt with; an alkaline metallic element added thereto.
A preferable example of the alkaline metallic element is potassium.
The catalyst for producing carbon mainly composed of at least either nickel or cobalt is improved in carbon producibility as compared with the conventional transition metal catalyst by adding the alkaline metallic element
The present invention also provides a method of producing carbon by bringing the aforementioned catalyst according to the present invention into contact with mixed gas containing a carbon source.
When employing a catalyst mainly composed of cobalt with potassium added thereto as the alkaline metallic element, the reaction temperature is preferably 350 to 550xc2x0 C., more preferably 410 to 430xc2x0 C.
When employing a catalyst mainly composed of nickel with potassium added thereto as the alkaline metallic element, the reaction temperature is preferably 400 to 610xc2x0 C., more preferably 480 to 600xc2x0 C.
Exemplary mixed gas serving as reaction gas for producing carbon contains carbon dioxide as the carbon source. By employing carbon dioxide as the carbon source, it is possible to cope with global warming. Alternatively, other carbon compounds may also be employed as the carbon source.
When containing carbon dioxide as the carbon source, the mixed gas preferably further contains a reductant for reducing carbon dioxide by catalytic reaction and producing carbon. An exemplary reductant is hydrogen. Alternatively, other reductants may also be employed.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.